Shock absorbing steering column unit for vehicle

ABSTRACT

In an impact absorbing type steering column apparatus for an automotive vehicle in which an upper column is fitted to a lower column fixed to a car body so as to absorb an impact energy upon a secondary collision while moving the upper column along the lower column towards a front side of the automotive vehicle, a low-friction material treatment is effected on one or both of slide surfaces of fitting portions of the two columns, or a sleeve subjected to the low-friction material treatment is interposed between the fitting portions thereof.

TECHNICAL FIELD

The present invention relates to an impact absorbing type steeringcolumn apparatus for an automotive vehicle.

BACKGROUND ARTS

In a steering column apparatus for an automotive vehicle, according to atelescopic type capable of adjusting a steering column in axialdirections, corresponding to a driving position (posture) of a driver,for example, an upper column is fitted in a telescopically slidablemanner to a lower column fixed to a car body.

Further, according to a non-telescopic type incapable of making thetelescopic adjustment, for instance, the upper column is so fitted tothe lower column fixed to the car body as not to slide at a normal time.

Moreover, an electric power steering type in a column assist system isthat an electric power assist apparatus is provided at a column portionbetween a steering wheel and an upper joint of an intermediate shaft,thus performing the steering assist.

By the way, when a secondary collision happens, the upper column ismoved for collapsing along the lower column fixed to the car bodytowards the front side of the automotive vehicle, and in the meantime avariety of impact absorbing means absorb impact energy.

A fitting length between the two columns upon collapsing has, however,become comparatively short over the recent years.

As a result, upon the secondary collision, just when the upper columngets collapsed and is to start moving towards the front side of theautomotive vehicle, the upper column might not necessarily smoothlyslide on the lower column.

Especially in the electric power steering type in the column assistsystem, it is difficult to ensure a space for collapsing due to aspatial influence of a motor, a deceleration mechanism, etc., and hencethe above tendency is conspicuous. Further, in the case of the electricpower steering type in the column assist system and in the telescopicadjustment system, the tendency described above become more conspicuous.

Further, a fitting angle of a steering wheel (which is an angle of asteering shaft to the horizon) is set as large as 30 degrees orthereabouts, depending on the automotive vehicles. In this case, anacting direction of an impact load towards the front side of theautomotive vehicle is not coincident with a slide direction of the uppercolumn at the fitting portions of the two columns, and consequentlyblocking (unsmoothed) force acts on between the fitting portions of thetwo columns. In this case also, the upper column might not necessarilysmoothly slide on the lower column.

Such being the case, if the fitting length between the two columns iscomparatively short, or even if the fitting angle of the steering wheelis large, there is demand for a smooth start of the movement of theupper column towards the front side of the automotive vehicle.

Moreover, when performing a telescopic operation, the operation involveseffecting a movement in the axial direction with one hand in a blockedstate, wherein operating force rises and a locked state occurs as thecase may be.

Note that for attaining a smooth start of the movement of the uppercolumn when collapsing, for example, a spacer formed of a resin isinterposed between the two columns according to Japanese Utility ModelApplication Laid-Open No. 1-172965, a spacer formed of super highpolymeric polyethylene is press-fitted in between the two columnsaccording to Japanese Patent Application Laid-Open No. 9-95245, and aspacer partially formed with a recessed portion and including a metalmesh coated with Teflon (registered trademark), is press-fitted inbetween the two columns according to Japanese Patent No. 2983130.

DISCLOSURE OF THE INVENTION

It is an object of the present invention, which was devised under suchcircumstances, to provide an impact absorbing type steering columnapparatus for an automotive vehicle that is capable of a smooth start ofa movement of an upper column towards a front side of the automotivevehicle even if a fitting length between a lower column and the uppercolumn when collapsing upon a secondary collision is comparativelyshort, and so on.

To accomplish the above object, in an impact absorbing type steeringcolumn apparatus for an automotive vehicle in which an upper column isfitted to a lower column fixed to a car body so as to absorb an impactenergy upon a secondary collision while moving the upper column alongthe lower column towards a front side of the automotive vehicle, thereis provided an improvement characterized in that a low-friction materialtreatment is effected on one or both of slide surfaces of fittingportions of the two columns.

Thus, according to the present invention, the low-friction materialtreatment is effected on one or both of the slide surfaces of thefitting portions of the two columns, and hence a slide load of the uppercolumn can be reduced by decreasing a coefficient of friction on theslide surfaces of the fitting portions of the two columns. Accordingly,if a fitting length between the two columns is comparatively short, oreven if a fitting angle of a steering wheel is large, a smooth start ofthe movement of the upper column towards the front side of theautomotive vehicle can be attained.

As a result, subsequent collapsing can be smoothly performed, therebyfacilitating control of the absorption of the impact energy. Further, asa consequence of the smooth start of the movement of the upper column,none of a blocking load affects the two columns, thereby enabling thecollapsing to be smoothly done.

Moreover, in the case of a telescopic adjustment system, handling isdone with one hand in a blocked (unsmoothed) state when performing theoperation for the telescopic adjustment, resulting possibly in a rise inoperating force. According to the present invention, however, thelow-friction material treatment is effected on one or both of the slidesurfaces of the fitting portions of the two columns, and therefore theoperating force for the telescopic adjustment can be reduced bydecreasing the coefficient of friction on the slide surfaces of thefitting portions of the two columns, whereby the operation for thetelescopic adjustment can be smoothly conducted.

Note that a collapsing stroke implies a collapsing length, and thecollapsing implies the absorption of the impact energy through plasticdeformation and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an impact absorbing type steering columnapparatus in a tilt/telescopic adjustment system in a first embodimentof the present invention;

FIGS. 2A and 2B are enlarged sectional views taken along the line A-Aand the line B-B in FIG. 1 (or FIG. 8), respectively;

FIG. 3 is a side view of the steering column apparatus shown in FIG. 1,illustrating a shortest telescopic adjustment state;

FIG. 4 is a view showing a state of an end of absorption of an impactcaused when a secondary collision happens;

FIG. 5 is a side view of an impact absorbing type steering columnapparatus in a tilt/telescopic adjustment system in a second embodimentof the present invention;

FIG. 6 is a sectional view taken along the line B-B in FIG. 5 or FIG.11;

FIGS. 7A-7C show a third embodiment of the present invention; FIG. 7A isa semi-sectional view of a sleeve; FIG. 7B is a partial sectional viewshowing a modified example of an inner column; FIG. 7C is a partialsectional view of a further modified example of the inner column;

FIG. 8 is a side view of an impact absorption type steering columnapparatus in the tilt/telescopic system according to a fourth embodimentof the present invention;

FIG. 9 is a side view of the steering column apparatus shown in FIG. 8,showing a shortest telescopic adjustment state;

FIG. 10 is a side view of the steering column apparatus shown in FIG. 8,showing a state in which the absorption of the impact generated upon thesecondary collision is terminated;

FIG. 11 is a side view of an impact absorption type steering columnapparatus in the tilt/telescopic system according to a fifth embodimentof the present invention;

FIG. 12A is a side view of an impact absorption type steering columnapparatus in the tilt/telescopic system according to a sixth embodimentof the present invention; FIG. 12B is a sectional view taken along theline b-b in FIG. 12A;

FIG. 13A is a side view of an impact absorption type steering columnapparatus in a non-telescopic adjustment system according to a seventhembodiment of the present invention; FIG. 13B is a rear view (showingthe front side as viewed from the rear side of the automotive vehicle)of the steering column apparatus shown in FIG. 13A;

FIGS. 14A-14C are semi-sectional views of the steering column accordingto an eighth embodiment of the present invention; FIG. 14A is thesemi-sectional view showing a first example thereof; FIG. 14B shows asemi-sectional view and a rear view illustrating a second examplethereof; FIG. 14C is the semi-sectional view showing a third examplethereof; and

FIGS. 15A-15D are semi-sectional views of the steering column accordingto the eighth embodiment of the present invention; FIG. 15A is thesemi-sectional view showing a fourth example thereof; FIG. 15B is asemi-sectional view showing a fifth example thereof; FIG. 15C is thesemi-sectional view showing a sixth example thereof; FIG. 15D is thesemi-sectional view showing a seventh example thereof.

THE EMBODIMENTS OF THE INVENTION

An impact absorbing type steering column apparatus of a tilt/telescopicadjustment type according to embodiments of the present invention, willhereinafter be described with reference to the drawings.

First Embodiment

FIG. 1 is a side view of the impact absorbing type steering columnapparatus of the tilt/telescopic adjustment type in a first embodimentof the present invention.

FIGS. 2A and 2B are sectional views taken along the line A-A in FIG. 1and the line B-B in FIG. 1, respectively.

FIG. 3 is a side view of the steering column apparatus shown in FIG. 1,illustrating a shortest position in a telescopic adjustment.

FIG. 4 is a view showing a state of an end of absorption of an impactcaused when a secondary collision happens.

As shown in FIGS. 1, 2A and 2B, the first embodiment illustrates anexample of a fastening lock mechanism of a center holding typetilt/telescopic adjustment apparatus. An inner column 1 is fitted in atelescopically slidable manner into an outer column 2. A steering shaft3 is rotatably supported within the two columns 1 and 2.

The outer column 2 is secured to a car body through proper fasteningmembers (unillustrated) by horizontally extending members 104 of a carbody sided bracket 4 of the fastening lock mechanism of thetilt/telescopic adjustment apparatus. As shown in FIG. 2A, the car bodysided bracket 4 integrally has a pair of side plate members 4 a and 4 brespectively formed with tilt adjustment grooves 5 a, 5 b and extendingin a perpendicular direction with the outer column 2 interposedtherebetween.

A ring-shaped member 6 is provided along an outer periphery of the outercolumn 2. The ring-shaped member 6 is constructed of a member 6 a takingsubstantially in a U-shape and a bolt 6 b for fastening both of lowerside ends of this member 6 a.

The outer column 2 is provided integrally with a pair of flanges 7 a, 7b anterior and posterior to the ring-shaped member 6. The flanges 7 a, 7b are held between the two side plate members 4 a, 4 b of the car bodysided bracket 4.

A lower end of the outer column 2 is formed with a slit 2 a extending inan axial direction between the flanges 7 a and 7 b. When one pair offlanges 7 a, 7 b are pinched and held by the two side plate members 4 a,4 b, the slit 2 a is closed, whereby the outer column 2 shrinks in itsdiameter. This contrivance enables fastening in a tilt/telescopicadjustment position in such a way that the outer column 2 presses theinner column 1.

A bolt 8 a is provided outwardly of one side plate member 4 a of the carbody sided bracket 4, and a front end of the bolt 8 a is fixed to thering-shaped member 6.

The bolt 8 a is provided with a manipulation lever 9 and a cam lockmechanism. The cam lock mechanism is structured of a first cam member 10rotating integrally with the manipulation lever 9 and a second cammember 11 that is non-rotational. The first cam member 10 moves in theaxial direction while a crest portion of the first cam member 10 engageswith a target cam portion of the second cam member 11 as the first cammember 10 rotates, thus locking therewith and unlocking therefrom. Thenon-rotational second cam member 11 and the bolt 8 a are constructedintegrally in terms of their rotational action. Namely, the bolt 8 a isnon-rotational. A thrust bearing 12 is provided between a head of thebolt 8 a and the manipulation lever 9.

A bolt 8 b is provided outwardly of the other side plate member 4 b ofthe car body sided bracket 4. An intermediate portion of the bolt 8 b isthread-engaged with the ring-shaped member 6, and a front end thereofpenetrates through the outer column 2 and engages with a telescopicadjustment groove 13 formed in the inner column 1. In thethus-constructed fastening lock mechanism of the tilt/telescopicadjustment apparatus, when fastened in the tilt/telescopic adjustmentposition, the manipulation lever 9 is rotated in one direction.Thereupon, the cam/lock mechanism acts to separate the first cam member10 and the second cam member 11 from each other, whereby the first cammember 10 presses the bolt 8 a outwards (towards the left in FIGS. 2Aand 2B), and the second cam member 11 presses one side plate member 4 aof the car sided bracket 4 inwards (towards the right in FIGS. 2A and2B).

The bolt 8 a pressed outwards (towards the left in FIGS. 2A and 2B)pulls inwards the bolt 8 b on the opposite side through the ring-shapedmember 6, whereby the bolt 8 b presses the other side plate member 4 bof the car body sided bracket 4 inwards (towards the left in FIGS. 2Aand 2B).

Thus, one pair of side plate members 4 a, 4 b of the car body sidedbracket 4 are respectively pressed inwards, as a result of this, onepair of flanges 7 a, 7 b are pinched and held by the side plate members4 a, 4 b, and the slit 2 a of the outer column 2 is closed, whereby theouter column 2 shrinks in its diameter. With this diametrical shrinkage,the outer column 2 presses the inner column 1, thereby enabling thefastening in the tilt/telescopic adjustment position.

In this way, the two columns 1, 2 are fastened evenly from both sides,and hence the center of the two columns 1, 2 can be invariably kept.

When released from the tilt/telescopic adjustment position, themanipulation lever 9 is rotated in the other direction, the cam/lockmechanism acts to make the first cam member 10 and the second cam member11 approach each other, whereby the first cam member 10 moves the bolts8 a inwards (towards the right in FIGS. 2A and 2B), and the second cammember 11 releases the pressing upon one side plate member 4 a of thecar body sided bracket 4, and opens one side plate member 4 a outwards(towards the left in FIGS. 2A and 2B).

As a result of the inward movement (towards the right in FIGS. 2A and2B) of the bolt 8 a, the bolt 8 b on the opposite side can be releasedthrough the ring-shaped member 6 from being pulled inwards (towards theleft in FIG. 2). The other side plate member 4 b of the car body sidedbracket 4 is thereby opened outwards (towards the right in FIGS. 2A and2B).

Thus, the pair of side plate members 4 a, 4 b of car body sided bracket4 respectively expand outwards, with the result that the pair of flanges7 a, 7 b expand outwards, whereby the inner column 1 can be releasedfrom being fastened by the outer column 2.

Next, in the first embodiment, as shown in FIG. 1, a low-frictionmaterial treatment is effected over at least a lengthwise range of thetelescopic adjustment on one or both of the slide surfaces of thefitting portions of the two columns 1, 2. The low-friction materialtreatment is one of baking of molybdenum disulfide, baking offluororesin, baking of a mixture of molybdenum disulfide andfluororesin, coating of a ceramic, a metal soap treatment, alow-friction plating treatment and coating of a lubricating agent suchas grease, etc. but is not limited to these treatments.

Further, the telescopic adjustment groove 13 is, as illustrated in FIGS.2A and 2B, a bottomed groove extending in the axial directions. Thetelescopic adjustment groove 13 is formed so that a groove width thereofbecomes gradually smaller as its position gets closer to an end portionfrom a central portion thereof. With this contrivance, in a sectionindicated by [EA], the front end of the bolt 8 b sequentially expandsthe telescopic adjustment groove 13, whereby the impact energy can beabsorbed. Note that the telescopic adjustment groove 13 may also be athrough-hole. The outer column 2 may be formed with a telescopicadjustment groove similar to the groove 13, with which the front end ofthe bolt 8 a engages, wherein both of the bolts 8 a and 8 b may absorbthe impact energy.

Supposing that, for example, when in a state (a telescopic neutralposition) shown in FIG. 1, a secondary collision is to happen, a loadequal to or larger than sustainable force is applied upon the fasteninglock mechanism in a tilt/telescopic adjustment position, the innercolumn 1 moves along the outer column 2 fixed to the car body towardsthe front side of the automotive vehicle, while the front end of thebolt 8 b engages with the telescopic adjustment groove 13.

When the inner column 1 moves towards the front side of the automotivevehicle and reaches a position (a shortest telescopic adjustmentposition) shown in FIG. 3, the front end of the bolt 8 b enters thesection (EA) where the groove width of the telescopic adjustment groove13 gradually decreases.

Thereafter, as seen in an illustrative transition from FIG. 3 to FIG. 4,the inner column 1 further moves towards the front side of theautomotive vehicle. On this occasion, the front end of the bolt 8 bsequentially expands the telescopic adjustment groove 13, therebygenerating a collapse load. The impact energy is thus absorbed. As shownin FIG. 4, when the inner column 1 moves down to the end of thetelescopic adjustment groove 13, the collapsing finishes.

Thus, according to the first embodiment, the low-friction materialtreatment is effected on one or both of the slide surfaces of thefitting portions of the two columns 1, 2, and hence the slide load ofthe inner column 1 can be reduced by decreasing a coefficient of thefriction on the slide surfaces of the fitting portions of the twocolumns 1, 2. Accordingly, if a fitting length between the two columns1, 2 is comparatively short, or even if a fitting angle of the steeringwheel is large, a smooth start of the movement of the inner column 1towards the front side of the automotive vehicle can be attained. Thelow-friction material treatment may be executed also on theslide-abutting surface shown by [EA] for absorbing the impact energy.

As a result, the subsequent collapsing can be smoothly performed,thereby facilitating the control of the absorption of the impact energy.Further, as a consequence of the smooth start of the movement of theinner column 1, none of a blocking load affects the two columns, therebyenabling the collapsing to be smoothly done.

Moreover, in the case of the telescopic adjustment system, if handledwith one hand when performing the operation for the telescopicadjustment, the movement of the inner column through within the outercolumn gets unsmoothed (blocked), resulting possibly in a rise in theoperating force for the telescopic adjustment. According to the firstembodiment, the low-friction material treatment is effected on one orboth of the slide surfaces of the fitting portions of the two columns 1,2, and therefore the operating force for the telescopic adjustment canbe reduced by decreasing the coefficient of friction on the slidesurfaces of the fitting portions of the two columns 1, 2, whereby theoperation for the telescopic adjustment can be smoothly conducted.

Second Embodiment

FIG. 5 is a side view of an impact absorbing type steering columnapparatus of a tilt/telescopic adjustment type in accordance with asecond embodiment of the present invention. In the second embodiment, anouter jacket 102 integral with the outer column 2, which will beexplained later on, is integral with a gearbox of an electric powerassist (Electric Power Steering (EPS)).

FIG. 6 is a sectional view taken along the line B-B in FIG. 5.

The second embodiment includes a column assist type electric powersteering (EPS) apparatus, and is an exemplification of a tilt/telescopicfastening lock mechanism of such a type that a fastening bolt directlypenetrates the outer jacket. The car body sided bracket 4 whosehorizontal portions 104 are fixed to the car body is integrally formedwith a pair of side plate members 4 a, 4 b extending in theperpendicular directions with the outer column 2 interposedtherebetween. A pair of embracing members 30 a, 30 b having large wallthickness and serving to embrace the inner column 1 and thus fasten thecolumn 1, are integrally formed at a rear end of the outer column 2between the side plate members 4 a, 4 b. Lower ends of the pair ofembracing members 30 a, 30 b respectively have flat portions swollensideways suitably for being pressed by the side plate members 4 a, 4 b,and a slit 30 c is formed in the middle between the embracing members 30a, 30 b.

A stopper bolt 31 is fitted in an upper portion of the pair of embracingmembers 30 a, 30 b. A lower end of the stopper bolt 31 engages with thetelescopic adjustment groove 13 of the inner column 1.

A fastening bolt 32 is inserted through the lower swollen portions ofthe pair of embracing members 30 a, 30 b between the pair of side plates4 a, 4 b of the car body sided bracket 4. An adjustment nut 33 isscrewed to a front thread portion of the fastening bolt 32, and themanipulation lever 9 is fitted through a fitting bolt 34 to theadjustment nut 33.

When fastened in the tilt/telescopic adjustment position, upon turningthe manipulation lever 9, the fastening bolt 32 moves to the left inFIG. 6, thereby pressing the pair of side plate members 4 a, 4 b of thecar body sided bracket 4 inwards respectively. As a result, the pair ofembracing members 30 a, 30 b are, at their lower swollen portions,compressed narrow to close the slit 30 c therebetween, whereby the innercolumn 1 can be fastened by pressing.

When in a tilt/telescopic cancellation, upon turning the manipulationlever 9 in the reversed direction, the fastening bolt 32 moves to theright in FIG. 6, thereby separating the pair of side plate members 4 a,4 b from each other and the pair of embracing members 30 a, 30 b fromeach other. With this separation, the pressing against the inner column1 can be cancelled. The low-friction material treatment may also beeffected on the slide-abutting surface for the energy absorption (EA).

Next, according to the second embodiment, as shown in FIG. 5, thelow-friction material treatment is effected over at least the lengthwiserange of the telescopic adjustment on one or both of the slide surfacesof the fitting portions of the two columns 1, 2. The low-frictionmaterial treatment is one of the baking of molybdenum disulfide, thebaking of fluororesin, the baking of the mixture of molybdenum disulfideand fluororesin, the coating of a ceramic, the metal soap treatment, thelow-friction plating treatment and the coating of the lubricating agentsuch as grease, etc. but is not limited to these treatments.

Further, the telescopic adjustment groove 13 is, as illustrated in FIG.6, a groove extending in the axial direction. The telescopic adjustmentgroove 13 is formed so that a groove width thereof becomes graduallysmaller as its position gets closer to an end portion from a centralportion thereof in the axial direction. With this contrivance, a lowerend of a stopper bolt 31 sequentially expands the telescopic adjustmentgroove 13, whereby the impact energy can be absorbed. Note that thetelescopic adjustment groove 13 may also be a bottomed groove.

Moreover, there may be provided a plurality of telescopic adjustmentgrooves 13 and a plurality f stopper bolts 31 in a peripheral direction,and their positions are shifted in the axial directions, whereby anoccurrence of a peak load may be prevented.

Assuming that, for instance, when in a state (the telescopic neutralposition) shown in FIG. 5, the secondary collision is to happen, theload equal to or larger than the sustainable force is applied upon thefastening lock mechanism in the tilt/telescopic adjustment position, theinner column 1 moves along the outer column 2 fixed to the car bodytowards the front side of the automotive vehicle, while the lower end ofthe stopper bolt 31 engages with the telescopic adjustment groove 13.

When the inner column 1 moves towards the front side of the automotivevehicle and reaches the shortest telescopic adjustment position, thelower end of the stopper bolt 31 enters a portion where the groove widthof the telescopic adjustment groove 13 is small.

Thereafter, the inner column 1 further moves towards the front side ofthe automotive vehicle. On this occasion, the lower end of the stopperbolt 31 sequentially expands the telescopic adjustment groove 13,thereby generating a collapse load. The impact energy is thus absorbed.When the inner column 1 moves down to the end of the telescopicadjustment groove 13, the collapsing finishes.

Thus, also in the second embodiment, the low-friction material treatmentis effected on one or both of the slide surfaces of the fitting portionsof the two columns 1, 2, and hence the slide load of the inner column 1can be reduced by decreasing the coefficient of the friction on theslide surfaces of the fitting portions of the two columns 1, 2.Accordingly, if the fitting length between the two columns 1, 2 iscomparatively short, or even if the fitting angle of the steering wheelis large, the smooth start of the movement of the inner column 1 towardsthe front side of the automotive vehicle can be attained.

As a result, the subsequent collapsing can be smoothly performed,thereby facilitating the control of the absorption of the impact energy.Further, as a consequence of the smooth start of the movement of theinner column 1, none of the blocking load affects the two columns,thereby enabling the collapsing to be smoothly done.

Moreover, in the case of the telescopic adjustment system, if handledwith one hand when performing the operation for the telescopicadjustment, the movement of the inner column through within the outercolumn gets unsmoothed (blocked), resulting possibly in the rise in thetelescopic operating force. According to the second embodiment, thelow-friction material treatment is effected on one or both of the slidesurfaces of the fitting portions of the two columns 1, 2, and thereforethe operating force for the telescopic adjustment can be reduced bydecreasing the coefficient of friction on the slide surfaces of thefitting portions of the two columns 1, 2, whereby the operation for thetelescopic adjustment can be smoothly conducted.

In the second embodiment illustrated in FIG. 5, the embracing members 30a, 30 b integral with the outer column 2 is made integral with the EPSgear box but may also be separated therefrom.

Third Embodiment

FIGS. 7A-7C show a third embodiment. FIG. 7A is a semi-sectional view ofa sleeve. FIG. 7B is a partial sectional view showing a modified exampleof the inner column. FIG. 7C is a partial sectional view of a furthermodified example of the inner column. Each of these sleeves is insertedin between the outer column 2 and the inner column 1 of the steeringcolumn apparatus as shown in, e.g., FIG. 5.

In the example in FIG. 7A, a sleeve 14, of which an inner surface issubjected to the low-friction material treatment, is fitted intoportions corresponding to the fitting portions of the two columns alongthe inner surface of the outer column 2 of the steering column apparatusshown in FIG. 5. The low-friction material treatment is one of thebaking of molybdenum disulfide, the baking of fluororesin, the baking ofthe mixture of molybdenum disulfide and fluororesin, the coating of aceramic, the metal soap treatment, the low-friction plating treatmentand the coating of the lubricating agent such as grease, etc. but is notlimited to these treatments.

Further, a single slit 14 a is formed in a circumferential area, therebyfacilitating the low-friction material treatment on the inner surface.This is because rounding work can be carried out after the low-frictionmaterial treatment. Moreover, the low-friction treatment may be effectedalso on the outer periphery of the inner column.

FIG. 7B shows an example in which a plurality of protruded streaks 15are formed in the peripheral direction of the inner column 1. Whencollapsed, the protruded streaks 15 on the inner column 1 arepress-fitted into the outer column 2, thereby generating the collapseload. The impact energy is thus absorbed. The low-friction material iscoated over at least one of the inner column and the outer column. Anarea formed with the protruded streaks on the inner column 1 serves asthe energy absorption (EA) range, while the left side area of the innercolumn 1 from the protruded streak 15 in FIG. 7B serves as thetelescopic adjustment range.

FIG. 7C shows an example in which the inner column 1 is formed so thatits diameter gradually becomes larger in the sequence of asmall-diameter portion 16 a, an intermediate-diameter portion 16 b and alarge-diameter portion 16 c. When collapsed, the small-diameter portion16 a, the intermediate-diameter portion 16 b and the large-diameterportion 16 c of the inner column 1 are sequentially press-fitted intothe outer column 2, thereby generating the collapse load. The impactenergy is thus absorbed. The inner column 1 may be formed in anelliptical shape suited for changing its diameter. The low frictionmaterial is coated over at least one of the inner column and the outercolumn.

As described above, according to the present invention, the impactabsorption system may be the system for press-fitting into the outercolumn 2, or may be the system for expanding the telescopic adjustmentgroove 13 as in the first and second embodiments, or may also be acombination of these systems. Other systems are available without beinglimited to those systems on condition that the energy absorption typesbe those utilizing the relative movement of the inner column to theouter column.

Fourth Embodiment

FIG. 8 is a side view of an impact absorption type steering columnapparatus of the tilt/telescopic type according to a fourth embodimentof the present invention.

FIG. 2A is a sectional view taken along the line A-A in FIG. 8. In thefourth embodiment, the tilt/telescopic adjustment mechanism is the sameas that in the second embodiment.

FIG. 9 is a side view of the steering column apparatus shown in FIG. 8,showing a shortest telescopic adjustment state.

FIG. 10 is a side view of the steering column apparatus shown in FIG. 8,showing a state in which the absorption of the impact generated upon thesecondary collision is terminated.

In the fourth embodiment, as illustrated in FIG. 8, a metallic ring 20formed of iron, etc. is press-fitted or otherwise into a predeterminedposition of an outer peripheral surface of the inner column 1. Anannular damper 21 formed of a rubber or a synthetic resin is providedintegrally with the metallic ring 20 on the side of the outer column 2.

As illustrated in FIG. 9, the metallic ring 20 and the damper 21, whenadjusted to the shortest telescopic adjustment state, act as a stopperfor regulating the telescopic slide by abutting on the outer column 2.Moreover, on this occasion, the damper 21 prevents abutting noisescaused by abutting on the outer column 2 and also restrains an impactthereof.

Further, supposing that the secondary collision happens when in thestate shown in FIG. 8, the load equal to or larger than the sustainableforce is applied upon the fastening lock mechanism in thetilt/telescopic adjustment position, the inner column 1 moves along theouter column 2 fixed to the car body towards the front side of theautomotive vehicle, while the front side end of the bolt 8 b engageswith the telescopic adjustment groove 13.

When the inner column 1 moves to some extent towards the front side ofthe automotive vehicle, the metallic ring 20 and the damper 21 impingeon the rear end of the outer column 2. Thereafter, as shown in FIGS. 9and 10, the inner column 1 further moves towards the front side of theautomotive vehicle. On this occasion, the metallic ring 20 frictionallyslides on the outer peripheral surface of the inner column 1 movingtowards the front side of the automotive vehicle while engaging with therear end of the outer column 2, thereby generating the collapse load.The impact energy is thus absorbed. As shown in FIG. 10, when the innercolumn 1 moves down to the end of the telescopic adjustment groove 13,the collapsing finishes.

From what has been discussed so far in the fourth embodiment, it ispossible to extremely easily to set and adjust the collapse load byadjusting the fitting state (the fastening state) of the metallic ring20.

Moreover, according to the fourth embodiment, as shown in FIG. 8, thelow-friction material treatment is effected on one or both of the slidesurfaces, especially at least on the collapse slide surface at thefitting portions of the two columns 1, 2. The low-friction materialtreatment may also be effected on the slide-abutting surface in theenergy absorption range. The low-friction material treatment is one ofthe baking of molybdenum disulfide, the baking of fluororesin, thebaking of the mixture of molybdenum disulfide and fluororesin, thecoating of a ceramic, the metal soap treatment, the low-friction platingtreatment and the coating of the lubricating agent such as grease, etc.but is not limited to these treatments.

Thus, according to the fourth embodiment, the low-friction materialtreatment is effected on one or both of the slide surfaces of thefitting portions of the two columns 1, 2, and hence the slide load ofthe inner column 1 can be reduced by decreasing the coefficient of thefriction on the slide surfaces of the fitting portions of the twocolumns 1, 2. Accordingly, if the fitting length between the two columns1, 2 is comparatively short, or even if the fitting angle of thesteering wheel is large, the smooth start of the movement of the innercolumn 1 towards the front side of the automotive vehicle can beattained.

As a result, the subsequent collapsing can be smoothly performed,thereby facilitating the control of the absorption of the impact energy.Further, as a consequence of the smooth start of the movement of theinner column 1, none of the blocking load affects the two columns,thereby enabling the collapsing to be smoothly done.

Moreover, in the case of the telescopic adjustment system, if handledwith one hand when performing the operation for the telescopicadjustment, the movement of the inner column through within the outercolumn gets unsmoothed (blocked), resulting possibly in the rise in thetelescopic operating force. In the fourth embodiment, the low-frictionmaterial treatment is effected on one or both of the slide surfaces ofthe fitting portions of the two columns 1, 2, and therefore theoperating force for the telescopic adjustment can be reduced bydecreasing the coefficient of friction on the slide surfaces of thefitting portions of the two columns 1, 2, whereby the operation for thetelescopic adjustment can be smoothly conducted.

Fifth Embodiment

FIG. 11 is a side view of an impact absorption type steering columnapparatus of the tilt/telescopic type according to a fifth embodiment ofthe present invention. In the fifth, the tilt/telescopic adjustmentmechanism is the same as that in the second embodiment.

FIG. 6 is a sectional view taken along the line B-B in FIG. 11.

In the fifth embodiment, as illustrated in FIG. 11, a metallic ring 20formed of iron, etc. is press-fitted or otherwise into a predeterminedposition on the inner column 1. A damper 21 formed of a rubber or asynthetic resin is provided integrally with the metallic ring 20 on theside of the outer column 2.

The metallic ring 20 and the damper 21, when adjusted to the shortesttelescopic adjustment state, act as a stopper for regulating thetelescopic slide by abutting on the outer column 2. Moreover, on thisoccasion, the damper 21 prevents abutting noises caused by abutting onthe outer column 2 and also restrains an impact thereof.

Further, if the secondary collision happens and when the inner column 1moves to some extent towards the front side of the automotive vehicle,the metallic ring 20 and the damper 21 impinge on the rear end of theouter column 2. Thereafter, the inner column 1 further moves towards thefront side of the automotive vehicle. On this occasion, the metallicring 20 frictionally slides on the outer peripheral surface of the innercolumn 1 moving towards the front side of the automotive vehicle whilebeing engaged and stopped with the rear end of the outer column 2,thereby generating the collapse load. The impact energy is thusabsorbed.

In the fifth embodiment, the outer jacket 102 integral with the outercolumn 2 is formed integrally with a housing of the electric powerassist (Electric Power Steering (EPS)) mechanism.

From what has been discussed so far in the fifth embodiment, it ispossible to extremely easily to set and adjust the collapse load byadjusting the fitting state (the fastening state) of the metallic ring20.

Moreover, according to the fifth embodiment, as shown in FIG. 11, thelow-friction material treatment is effected on one or both of the slidesurfaces of the fitting portions of the two columns 1, 2. Thelow-friction material treatment is as described above and effected in atleast the telescopic slide-abutting range anterior to the ring and mayalso be effected posterior to the ring.

Thus, according to the fifth embodiment, the low-friction materialtreatment is effected on one or both of the slide surfaces of thefitting portions of the two columns 1, 2, and hence the slide load ofthe inner column 1 can be reduced by decreasing the coefficient of thefriction on the slide surfaces of the fitting portions of the twocolumns 1, 2. Accordingly, if the fitting length between the two columns1, 2 is comparatively short, or even if the fitting angle of thesteering wheel is large, the smooth start of the movement of the innercolumn 1 towards the front side of the automotive vehicle can beattained. As a result, the subsequent collapsing can be smoothlyperformed, thereby facilitating the control of the absorption of theimpact energy.

Moreover, in the case of the telescopic adjustment system, if handledwith one hand when performing the operation for the telescopicadjustment, the movement of the inner column through within the outercolumn gets unsmoothed (blocked), resulting possibly in the rise in thetelescopic operating force. In the fifth embodiment, the low-frictionmaterial treatment is effected on one or both of the slide surfaces ofthe fitting portions of the two columns 1, 2, and therefore thetelescopic operating force can be reduced by decreasing the coefficientof friction on the slide surfaces of the fitting portions of the twocolumns 1, 2, whereby the telescopic operation can be smoothlyconducted.

Sixth Embodiment

FIG. 12A is a side view of an impact absorption type steering columnapparatus of the tilt/telescopic type according to a sixth embodiment ofthe present invention. FIG. 12B is a sectional view taken along the lineb-b in FIG. 12A.

In the sixth embodiment, the metallic ring 20 is fitted on an outerperipheral surface of an inner column 40 subjected to the low-frictionmaterial treatment described above. The metallic ring 20 is constructedof a pair of half-ring segments 20 a, 20 b into which the ring 20 issegmented by half. The pair of half-ring segments 20 a, 20 b arefastened at their upper and lower ends by a pair of bolts 51, 52. Adamper 21 formed of a synthetic resin is covered over the pair ofhalf-ring segments 20 a, 20 b.

Thus, a gap between the two pieces of half-ring segments 20 a, 20 b ischanged by varying the fastening force of the pair of bolts 51, 52,whereby the fitting state (fastening state) of the metallic ring 20 canbe adjusted and the collapse load can be set and adjusted much easierthan in the embodiments discussed above.

Seventh Embodiment

FIG. 13A is a side view of an impact absorption type steering columnapparatus of a non-telescopic type according to a seventh embodiment ofthe present invention. FIG. 13B is a rear view (showing the front sideas viewed from the rear side of the automotive vehicle) of the steeringcolumn apparatus shown in FIG. 13A.

The impact absorption type steering column apparatus in the seventhembodiment comes under a non-telescopic adjustment system incapable ofmaking the telescopic adjustment, wherein an inner column 61 is sopress-fitted into an outer column 62 formed integrally with a car bodysided bracket 60 as not to slide thereon at a normal time, and asteering shaft 63 is rotatably supported within the two columns 61, 62.If the secondary collision happens, however, a contrivance is that theinner column 61 becomes movable along the outer column 62 towards thefront side of the automotive vehicle.

Next, in the seventh embodiment, the metallic ring 20 formed of iron,etc. is press-fitted or otherwise into a predetermined position on theinner column 61. The damper 21 formed of a rubber or a synthetic resinis provided on the metallic ring 20 on the side of an outer column 62.

If the secondary collision happens and when the inner column 61 moves tosome extent towards the front side of the automotive vehicle, themetallic ring 20 and the damper 21 impinge on the rear end of the outercolumn 62. Thereafter, the inner column 61 further moves towards thefront side of the automotive vehicle. On this occasion, the metallicring 20 frictionally slides on the outer peripheral surface of the innercolumn 61 moving towards the front side of the automotive vehicle whileengaging with the rear side end of the outer column 62, therebygenerating the collapse load. The impact energy is thus absorbed.

From what has been discussed so far in the seventh embodiment, it ispossible to extremely easily to set and adjust the collapse load byadjusting the fitting state (the fastening state) of the metallic ring20.

Moreover, according to the seventh embodiment, as shown in FIGS. 13 aand 13B, the low-friction material treatment is effected on one or bothof the slide surfaces of the fitting portions of the two columns 61, 62.The low-friction material treatment is as described above. Thelow-friction material treatment is effected on the press-fittingportions of the two columns 61, 62 or on the energy absorbing portion.

In the seventh embodiment, the low-friction material treatment iseffected on one or both of the slide surfaces of the fitting portions ofthe two columns 61, 62, and hence the slide load of the inner column 61can be reduced by decreasing the coefficient of the friction on theslide surfaces of the fitting portions of the two columns 61, 62.Accordingly, if the fitting length between the two columns 61, 62 iscomparatively short, or even if the fitting angle of the steering wheelis large, the smooth start of the movement of the inner column 61towards the front side of the automotive vehicle can be attained. As aresult, the subsequent collapsing can be smoothly performed, therebyfacilitating the control of the absorption of the impact energy.

Eight Embodiment

FIGS. 14A-14C are semi-sectional views of the steering column in aneighth embodiment of the present invention. FIG. 14A is thesemi-sectional view showing a first example thereof. FIG. 14B shows asemi-sectional view and a rear view illustrating a second examplethereof. FIG. 14C is the semi-sectional view showing a third examplethereof. The eighth embodiment can be applied to the fourth throughseventh embodiments discussed above.

FIGS. 15A-15D are semi-sectional views of the steering column in theeighth embodiment of the present invention. FIG. 15A is thesemi-sectional view showing a fourth example thereof. FIG. 15B is asemi-sectional view showing a fifth example thereof. FIG. 15C is thesemi-sectional view showing a sixth example thereof. FIG. 15D is thesemi-sectional view showing a seventh example thereof.

In FIGS. 14A-14C and 15A-15D, the right side corresponds to the rearside of the automotive vehicle, while the left side corresponds to thefront side of the automotive vehicle. In the respective Figures, theconfigurations on the front and rear sides of the automotive vehicle arethe same as the configurations of the front and rear sides of the ring20 and of the damper 21 in FIG. 11. In the case of the eighthembodiment, when the collision happens, the ring 20 impinges on theouter jacket, subsequently the collapsing progresses to such an extentthat the outer jacket impinges on the ring 70, thereby absorbing theenergy.

In the first example in FIG. 14A, in addition to the metallic ring 20and the damper 21 that are press-fitted as in the fourth embodiment,another metallic ring 70 is provided in a different position on thesteering column 81 in the axial directions.

The second example in FIG. 14B is that the steering column 81 is formedwith four lines of protruded streaks 82 spaced equally in the peripheraldirection. Each of the protruded streaks 82 extends in the axialdirections. The metallic ring 20 and the damper 21 are press-fitted ontothe outer peripheral portions of these protruded streaks 82. Note thatthe protruded streaks may be a plastically deformable member as shown inthe Figure and may also be formed by cut-raising.

The third example in FIG. 14C is that the same metallic ring 20 anddamper 21 as those in the fourth embodiment are fitted onto the portionsof the protruded streaks 82 on the front side of the automotive vehicle.With this contrivance, resistance caused by the frictional slide isincreased stepwise, thereby augmenting the collapse load.

In the fourth example on FIG. 15A, the steering column 81 is constructedof a small-diameter portion 81 a, an intermediate-diameter portion 81 band a large-diameter portion 81 c. The same metallic ring 20 and damper21 as those in the fourth embodiment are fitted onto the small-diameterportion 81 a. Owing to this contrivance, the resistance caused by thefrictional slide is increased at three stages, thereby furtheraugmenting the collapse load. Moreover, the collapsing characteristiccan be changed as intended in a way that properly changes lengths of thelarge-, intermediate- and small-diameter portions.

The fifth example in FIG. 15B is such that a tapered portion 81 d isformed between the small-diameter portion 81 a and the large-diameterportion 81 c, and the metallic ring 20 and the damper 21 are fitted ontothe small-diameter portion 81 a. With this contrivance, the resistancecaused by the frictional slide is gradually increased, thereby furtheraugmenting the collapse load.

The sixth example in FIG. 15C is that the steering column 81 has themetallic ring 20 that is made thin in its wall thickness on the rearside of the automotive vehicle, and is formed with a resistance-escapehole 83. Owing to this contrivance, the resistance caused by thefrictional slide is reduced, thus attaining a scheme of decreasing thecollapse load.

In the seventh example in FIG. 15D, the steering column 81 has themetallic ring 20 that is made thin in its wall thickness of amajor-diametrical portion thereof on the rear side of the automotivevehicle. With this contrivance, the resistance caused by the frictionalslide is reduced, thus attaining a scheme of decreasing the collapseload.

It is to be noted that the present invention can be modified in avariety of forms without being limited to the embodiments discussedabove. The present invention can be applied to an electric powersteering system and is highly effective in a column type electric powersteering particularly because of difficulty of setting a sufficientamount of collapsing. Moreover, the present invention is also applicableto a tilt type and a telescopic type.

As explained above, according to the present invention, if the steeringcolumn apparatus is of the telescopic adjustment type, the low-frictionmaterial treatment is effected on one or both of the slide surfaces ofthe fitting portions of the telescopic adjustment portions between thetwo columns. Then, if the steering column apparatus is one of thenon-telescopic adjustment type, the low-friction material treatment iseffected on the press-fitting portions of the two columns, and it istherefore possible to reduce the slide load of the upper column byreducing the coefficient of friction on the slide surfaces of thefitting portions of the two columns. Accordingly, if the fitting lengthbetween the two columns is comparatively short, or even if the fittingangle of the steering wheel is large, the smooth start of the movementof the upper column towards the front side of the automotive vehicle canbe attained.

As a result, the subsequent collapsing can be smoothly performed,thereby facilitating the control of the absorption of the impact energy.Further, as a consequence of the smooth start of the movement of theupper column, none of the blocking load affects the two columns, therebyenabling the collapsing to be smoothly done.

Moreover, in the case of the telescopic adjustment type, if handled withone hand in the unsmoothed state when performing the telescopicoperation, resulting presumably in the rise in the operating force.According to the present invention, however, the low-friction materialtreatment is effected on one or both of the slide surfaces of thefitting portions of the two columns, and therefore the telescopicoperating force can be reduced by decreasing the coefficient of frictionon the slide surfaces of the fitting portions of the two columns,whereby the telescopic operation can be smoothly conducted.

1. In an impact absorbing type steering column apparatus for anautomotive vehicle in which an upper column is fitted to a lower columnfixed to a car body so as to absorb an impact energy upon a secondarycollision while moving said upper column towards a front side of theautomotive vehicle, an improvement characterized in that a low-frictionmaterial treatment is effected on one or both of slide surfaces offitting portions of said two columns.
 2. An impact absorbing typesteering column apparatus for an automotive vehicle according to claim1, wherein said steering column apparatus is of an electric powersteering type of a column assist type.
 3. An impact absorbing typesteering column apparatus for an automotive vehicle according to claim1, wherein said steering column apparatus is of an electric powersteering type of a column assist type, and is capable of making atelescopic adjustment.
 4. In an impact absorbing type steering columnapparatus for an automotive vehicle in which an upper column is fittedto a lower column fixed to a car body so as to absorb an impact energyupon a secondary collision while moving said upper column towards afront side of the automotive vehicle, an improvement characterized inthat a sleeve subjected to a low-friction material treatment isinterposed between fitting portions of said two columns.
 5. An impactabsorbing type steering column apparatus for an automotive vehicleaccording to claim 1, wherein the low-friction material treatment is oneof baking of molybdenum disulfide, baking of fluororesin, baking of amixture of molybdenum disulfide and fluororesin, coating of a ceramic, ametal soap treatment, a low-friction plating treatment and coating of alubricating agent.
 6. An impact absorbing type steering column apparatusfor an automotive vehicle according to claim 2, wherein the low-frictionmaterial treatment is one of baking of molybdenum disulfide, baking offluororesin, baking of a mixture of molybdenum disulfide andfluororesin, coating of a ceramic, a metal soap treatment, alow-friction plating treatment and coating of a lubricating agent.
 7. Animpact absorbing type steering column apparatus for an automotivevehicle according to claim 3, wherein the low-friction materialtreatment is one of baking of molybdenum disulfide, baking offluororesin, baking of a mixture of molybdenum disulfide andfluororesin, coating of a ceramic, a metal soap treatment, alow-friction plating treatment and coating of a lubricating agent.
 8. Animpact absorbing type steering column apparatus for an automotivevehicle according to claims 4, wherein the low-friction materialtreatment is one of baking of molybdenum disulfide, baking offluororesin, baking of a mixture of molybdenum disulfide andfluororesin, coating of a ceramic, a metal soap treatment, alow-friction plating treatment and coating of a lubricating agent.